Saturday, 12 December 2020

Fresh drifts often deposited on surface hoar, making them highly prone to triggering

 Rigorously circumvent fresh drifts in steep terrain


During a night of clear skies on Thursday/Friday (10-11 December) surface hoar formed on the snowpack in widespread areas of Tirol. This now lurks atop an already cold, loosely-packed snow surface, at least in the major areas of precipitation, since wind impact terminated during the last phase of the most recent snowfall.


The glittering crystals are surface hoar. As soon as these are blanketed by snowdrifts, it becomes an extremely trigger-sensitive weak layer for slab avalanches. East Tirolean Tauern  (photo: LWD Tirol, 11.12.2020) 


Yesterday (11 December) winds at at high altitudes on the Main Alpine Ridge and in the typical foehn-exposed lanes intensifed noticeably. Snow plumes bore witness to the snow transport taking place. The snowdrift accumulations which were generated are in general extremely prone to triggering.


Snow plumes on Main Alpine Ridge (photo: LWD Tirol, 11.12.2020)


Therefore: caution is currently imperative towards freshly generated snowdrifts. Wherever the wind continues to transport the snow, small-to-medium naturally triggered avalanches are possible.

(Apart from wind impact, you can still enjoy superb powder snow, particularly at intermediate altitudes in the regions where there has been heavy snowfall.)